Relay



oci. 16, 192s.

P. MBCGAHAN RELAY Filed June 1.o', 1925 INVENTOR P60/Mac: aw

ATTORNEY Patent@ oa. 16,1928.

rana-maenner, or nAsT PITTSBURGH,

-EENNSYL'VANIL ALSSIGNOR T0 WESTING- HOUSE ELECTRIC 'I ANUFACTURING COMPANY, A CORPORATION 0E PENNSYL- VARIA.

RELAY.

Application led June 10, 1925. Seal No. $6,109. v

My invention relates to electroresponsive devices, and particularlyto electromagnetic relays.

One object of my invention is to provide a relay that shall be particularly adapted for `the short-circuit protection of distribution systemsin which the adjustment remains unchanged ordiierent values of load current traversing the system.

Another object o my invention is to pro-v vide a surge-'responsive relay that shall have two cooperating members normally in a delinite relation, irrespective of the current traversing the device, the normal relation oi which is changed upon a surge of current through the device.- v

A further object of my invention is to provide a relay'that shall have two independently movable Velements operated by an in. duction-motor means and operatively"y connected by a resilient means and'so damped in operation as to obtain a. predetermined relativev movement thereof, depending uponV the energization of the actuating means.

Vllt has been customary to employ overcurrent relays for the short-circuit protec tion of distribution systems which operated when the current Atraversing the system reached a predetermined abnormal value. In many instances,however,I suehrelays are unsatisfactory because of the variation in the value of the short-circuit current on Aaccount of changes in connected generator capacity. If the generator capacity of a system is reduced d of riods of light load, Vwhich may recur daile, it is evident that the shortfcircuit current' during such periods may be less or slightly greater than the load current during the peak load. The use of-an `over-current relay in such a system, therefore, provides no protection` during periods of light? load unless the adjustment of the relay is changed by the station operator. In accordance with my invention, a. rela which is responsive to short-circuits mi su den surges of current only is provided to obviate the aforementioned The relay acmprseentwo contact 1.pliembers having norm a 'te spaced ation, irrespective .of the value of the Yload current. The

contact members are responsive to the current traversing the'relay butfhave different time characteristics. Upon a surge of current, thereforefthe contact members are engaged to close a :circuit for tripping a ein cuit-interrupter or other'purpose. Preferably, both contact members are vdriven by a single'actuating means, a resilient connection being interpoI ed between the actuatingy means and the co heaviest damping.

The nature of my invention may be 4understood by V reference to the accompanying drawing, the single figure of which is a view, in perspective, of a relay embodying my inf vention. y lteferringfto the drawing, the relay comprlses an actuatingmeans l energized from a circuit 2 and controlling cont-)act members 3 under predetermined conditions in the circuit. The. actuating means is of the induc- .tion-motor type and comprises. an electromagnet 4 connected to acurrent transformer 5 in the circuit 2 and controlling a pivoted armature vmember 6. A spring 7 and a damping magnet 8 are provided tor 'con trolling vthe movement of the armature member 6. Connected to the armature member 6 through a spring 9 is a second pivoted disc tact member having the member l0, one of the Contact members 3 jbeing operatively connected to, and movable with, each. disc member. means, such as the damping means l1, are provided for controlling the movement of the disc member 10, the damping action on vthe disc member 10 being greater than that Suitable damping on the disc member 6. The disc member 10 l may have a greater mass than-the disc mem'- ber 6 or maybe mechanically or electrically damped instead of, or in addition to, being magnetically damped.

The electromagnet 4 is energized in -accordancev. with the lcurrent traversing the circuit 2' and actuates the armature member "6 against the restraining torque of the spring 7 an amount proportional to the cur- 'rent in'said circuit. The jsecond disc mem- .ber 10, being controlled by the armature member 6, also assumes aposition. dependent upon the current flowing in the circuit 2, but,

by reason of the fact that' it is heavily y damped and is driven through the resilient connection 9, the movements of the disc member are retarded with respect to those of is important.

the armature member 6. I

The contact members 3 traverse the same path and, under normal 'current conditions, ave a definite spaced relation With'respect to each other. V,If the current traversing the' `circuit 2 changes by reason of a change in' load thereon, the relation of thecontact members 3 remains unchanged, although, temporarily, the contact vmembers approach or recede from each other, dependingupon the amount ot' the change in load and whether the change is an increase or a decrease.

If a short-circuit occurs inthe circuit v2, however, the sudden increase of current actuates the armature member 6 in ,such

direction as to cause the contactmembers 3A to engage. The engagement of the Contact members ,i3 may be utilized to open the circuit 2, to yoperate an alarm, or for any other desired purpose.

The operation of the relay is not aiected by -the load on the circuit 2 or by the -connected generator capacity. In many applications of rotective relays, this feature or instance, if the circuit 2 is a railway distribution circuit on which the load varies widely, it is desirablefto provide a relay'vhichjis as sensitive to short-circuits during periods of light load as during periods of heavy load. Furthermore, if the' connected generator capacity is reduced durin periods of light load, it may happen that the short-circuit current during such periods is even less than the full-load current during a peak load. It is apparent that the -relay described is satisfactory `for this application, inasmuch as the adjustment is not affected'by the load, and the engagement of the contact membersis eiected upon a shortcircuit or heavy surge of current, irrespective of the actual value ozf such current.

`While I have illustrated one embodiment 'offmy invention, in order that the same may be readily understood, I do not consider that it is limited to the precise details shown and described, and, accordingl ,'I do -not wish to be limited except as in icated in the appended claims.

I claim as .my invention Y 1. In comb `nation with an electric circuit, a relay comprising a. rotatable armature having a contact secured thereto, inductive means for effecting the rotation thereof responsive to load conditions in said circuit, a second rotatable armature having a contact secured thereto in the path of movement ot said first Contact, a resilient driving conncction between said armatures, and means .whereby said contacts are maintained in spaced relation during normal variations in load on said circuit and aremoved into contacting relation responsive to an abnormal 05 increase in load. Y

2. In combination with an electric circuit, an armature` rotatable in response to thevaluefof current traversing Ysaid circuit, a contact member secured to said armature, a second'contact member and means for mount; ing the same'for movement in the path of movement of the first contact, and means -for maintaining said contacts in s aced relation during normal' variations in oad, and for 75 Ythe occurrence of an abnormal variation.

In testimony. whereof,'I have hereunto submy vname this 5th dav or June, 1925.

PAUL MAOGAHAN. 

